Cylinders of a variable displacement engine (VDE) may be deactivated to improve engine fuel consumption during low engine load conditions. Cylinders may be deactivated by closing intake and exhaust valves of the deactivated cylinders over an entire cycle of the engine. Further, fuel flow may be ceased to the deactivated cylinders. Output of engine cylinders that remain active is increased to provide the desired engine torque and compensate for torque lost due to cylinder deactivation. However, it may be difficult to control engine torque during deactivating of engine cylinders. One way to control engine torque during cylinder deactivation is to retard spark timing. Excess engine torque may be reduced via retarding spark timing, but engine fuel consumption during cylinder deactivations may be higher than is desired when the cylinders are combusting a stoichiometric mixture. This is because fuel consumption increases as cylinder charge increases, and cylinder charge may be greater than is desired when cylinders are being deactivated.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine operating method, comprising: adjusting a state of an engine volumetric efficiency actuator to increase engine volumetric efficiency while adjusting a state of a central throttle to maintain engine air flow via a controller in response to a request to deactivate one or more engine cylinders, the position of the engine volumetric efficiency actuator adjusted before deactivating the one or more engine cylinders.
By adjusting a position of an engine volumetric efficiency actuator and a central throttle, the technical result of improved engine air flow control during cylinder deactivation events may be provided. For example, a position of a charge motion control valve may be adjusted in response to a request to deactivate engine cylinders. Throttle position may also be adjusted while the charge motion control valve position is being adjusted to maintain engine air flow. A reduced amount of spark retard may be used to maintain engine torque during the cylinder deactivation transition.
The present description may provide several advantages. Specifically, the approach may improve engine torque control during cylinder deactivation events. Further, the approach may provide improved engine air flow control during cylinder deactivation events. Further still, the approach may improve engine emissions during cylinder deactivation events.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.